Surface modification of TiO2 by a ruthenium(II) polypyridyl complex via silyl-linkage for the sensitized photocatalytic degradation of carbon tetrachloride by visible irradiation

A new ruthenium(II) photosensitizer, [RuII(py-pzH)3]2+ (where py-pzH=3-(2-pyridyl)pyrazole), has been synthesized. The complex displayed outstanding excited state redox properties (estimated RuIII/RuII*1.24 V vs. NHE) and was expected to sensitize the injection of electrons into the conduction band of anatase TiO2 upon visible irradiation. The photosensitizer was anchored onto the surface of anatase TiO2 particles via in situ silylation. The silyl-linkage displayed excellent stability in both aqueous media, over a wide pH range, and in common organic solvents. The resultant material, TiO2-[RuII(py-pz-Si) 3], was found to be able to mediate degradation of CCl4 in neutral aqueous medium under broad band visible irradiation ((lambda) >450 nm). The relation between the rate of degradation and concentration of substrate was explored and the mechanism of the photodegradation of the perhalogenated organic was discussed.